The objectives of this research are: to study the toxic effects of drugs on the corneal endothelium, to determine the limits of mechanical trauma to the endothelium; to develop improved methods of testing functional capacity of the endothelium. To accomplish these goals existing, previously proven laboratory techniques will be used: in vitro perfusion, photography, light and electron microscopy. New techniques will be developed. These will include in vivo testing, improved instrumentation for corneal measurement and endothelial cell photography, corneal stress testing for endothelial function and electron microscopic changes caused by toxic substances.